1. Field of the Invention
The present invention relates to apparatus and systems for treating surfaces of laminated semiconductor substrates or liquid crystal glass substrates and the like (hereinafter, simply referred to as a wafer), and particularly to an apparatus and a system for performing surface treatment of wafers in which the wafers are dipped into treatment solution and composition of the treatment solution is changed, and a gate device for chemical agent included in the apparatus and the system.
2. Description of the Related Art
Cleaning of wafers greatly contributes to the improvement of the yield of semiconductor devices, for example, by removing contaminations from the wafers. A conventional technique of this kind is disclosed in Japanese Patent Publication No. 2-13459 (Japanese application No. 60-243025, filed on Oct. 31, 1985, Japanese Patent Laying-Open No. 61-295635, layed open on Dec. 26, 1986, corresponding to U.S. Pat. No. 4,633, 893, U.S. Ser. No. 747894 filed in the United States in Jun. 24, 1985). Referring to FIG. 1, a wafer treatment apparatus described in the document includes a wafer treatment bath 101, and a treatment solution supplying unit 104 for supplying a treatment solution 102 into wafer treatment bath 101.
Treatment solution supplying unit 104 includes a treatment solution drawing line 103 communicating with a treatment solution input port of wafer treatment bath 101, and chemical agent containers 106A-106D communicating with treatment solution drawing line 103 through chemical agent supplying lines 107A-107D and chemical agent introducing valves 108A-108D on the upstream of wafer treatment bath 101 for containing plural kinds of chemical agents Q.sub.A - Q.sub.D.
Etching agents such as hot sulfuric acid and hydrogen fluoride, or demineralized water, for example, are contained in chemical agent containers 106A-106D.
Wafer treatment bath 101 can be hermetically closed except for an inlet port and an outlet port for treatment solution. The outlet port communicates with drain 111.
Referring to FIG. 1A, wafers W are loaded in a cassette 51 and carried into wafer treatment bath 101 to be subjected to surface treatment. A space for accommodating a plurality of wafers W is formed inside cassette 51. Groves 52 for holding edges of wafers W are formed on side portions of the space.
The conventional apparatus shown in FIG. 1 operates as follows. Before treatment, cassette 51 in which wafers W are provided is carried into wafer treatment bath 101. Wafer treatment bath 101 is hermetically closed. Selectively controlling respective chemical agent introducing valves 108A-108D to open or close the same, desired chemical agents Q.sub.A - Q.sub.D are introduced into treatment solution drawing line 103. The introduced chemical agents are mixed and flow into wafer treatment bath 101. The surface of wafer W is treated with the flowing treatment solution. The treatment solution flows from the inlet to the outlet of wafer treatment bath 101 and let out into drain 111 from the outlet.
When the position of the treatment solution is to be changed in the course of the treatment, states of chemical agent introducing valves 108A-108D are selectively changed. In this case, the treatment solution in which the composition is changed flows into wafer treatment bath 101 following the treatment solution before the change and smoothly displace the same from wafer treatment bath 101. In the document, it is described that this is because a plug flow of the treatment solution is formed in wafer treatment bath 101.
After finishing the wafer treatment, chemical agent introducing valves 108A-108D are all closed. The treatment bath 101 is emptied. A wafer take-out port not shown provided in treatment bath 101 is opened and cassette 51 is taken out.
According to the conventional apparatus, when treatment solution 102 in treatment bath 101 is to be replaced with another treatment solution, the replacement can be completed in a short time. Accordingly, rapid surface treatment can be performed. Also, in substituting treatment solution 102 in bath 101, it is not necessary to draw all the treatment solution 102 from bath 101. Accordingly, wafers W never touch the air during treatment, so that troubles such as formation of an oxidized film on its surface will not occur.
However, the conventional apparatus still has the following problems to be solved. In this apparatus, quantities of chemical agents introduced into treatment solution 103 may fluctuate according to the fluctuations of the inner pressure in chemical agent containers 106A-106D and quantities of chemical agents remaining inside when introducing chemical agents Q.sub.A - Q.sub.D into treatment solution drawing line 103. Accordingly, demineralized water and chemical agents can not be precisely proportioned so that good surface treatment may not be applied to wafers W.
The conventional apparatus also has other problems to be solved as described below. Wafer treatment bath 101 is hermetically closed during treatment. Accordingly, it is necessary to draw all the treatment solution 102 from treatment bath 101 when loading wafers W into treatment bath 101 before treatment and taking out the same therefrom after the treatment. Furthermore, an outlet port must be provided in wafer treatment bath 101 and a mechanism is required for automatically opening and closing the outlet port when all the treatment solution is drawn out of bath 101. Such a mechanism is so complex that the process of manufacturing the apparatus and the method of operating the same become unnecessarily complex. The time required before and after the treatment also increases and the surface treatment of wafers is not conducted rapidly enough.
Also, the surfaces must be rapidly dried after surface treatment using the conventional apparatus. Accordingly, there has been a great demand for a system capable of integrally performing these works.